[patch 1/2]compaction: check migrated page number

[Shaohua Li <shli@kernel.org>]

isolate_migratepages_range() might isolate none pages, for example, when
zone->lru_lock is contended and compaction is async. In this case, we should
abort compaction, otherwise, compact_zone will run a useless loop and make
zone->lru_lock is even contended.

Signed-off-by: Shaohua Li <shli@fusionio.com>
---
 mm/compaction.c |    2 ++
 1 file changed, 2 insertions(+)

Index: linux/mm/compaction.c
===================================================================
--- linux.orig/mm/compaction.c	2012-08-22 09:51:39.295322268 +0800
+++ linux/mm/compaction.c	2012-09-06 14:46:13.923144263 +0800
@@ -402,6 +402,8 @@ isolate_migratepages_range(struct zone *
 
 	trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
 
+	if (!nr_isolated)
+		return 0;
 	return low_pfn;
 }
 

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>